The present invention relates to a three-piece solid golf ball. More particularly, it relates to a three-piece solid golf ball, of which flight distance is improved by accomplishing high launch angle and low spin amount in initial flight performance, while maintaining soft and good shot feel when hit at low head speed.
In golf balls commercially selling, there are solid golf balls such as two-piece golf ball, three-piece golf ball and the like, and thread wound golf balls. Recently, the two-piece golf ball and three-piece golf ball, of which flight distance can be improved while maintaining soft and good shot feel at the time of hitting as good as the conventional thread wound golf ball, generally occupy the greater part of the golf ball market. Three-piece golf ball have good shot feel while maintaining excellent flight performance, because they can vary hardness distribution and design of golf balls, when compared with the two-piece golf ball.
The three-piece solid golf balls are obtained by inserting an intermediate layer between the core and the cover layer constituting the two-piece solid golf ball and have been described in Japanese Patent Kokai Publication Nos. 313643/1997, 305114/1998 and Japanese Patent Nos. 2570587 and 2658811. In the golf balls, it has been attempted to compromise the balance of flight performance and shot feel at the time of hitting by using thermoplastic resin, such as ionomer resin, thermoplastic elastomer or mixtures thereof, for the intermediate layer, to adjust a hardness, hardness distribution and the like of the core, intermediate layer and cover to proper ranges.
In Japanese Patent Kokai Publication No. 313643/1997, a three-piece solid golf ball, of which an intermediate layer is placed between a core and a cover is described. The core has a center hardness in JIS-C hardness of not more than 75 and has a surface hardness in JIS-C hardness of not more than 85, the surface hardness is higher than the center hardness by 5 to 25, a hardness of the intermediate layer is higher than the surface hardness of the core by less than 10, and a hardness of the cover is higher than the hardness of the intermediate layer.
In Japanese Patent No. 2570587, a multi-piece solid golf ball which comprises a multi-layer structured solid core composed of an inner core and at least one layer of outer core, and a cover is described. The outer core has a Shore D hardness of 30 to 50 and is mainly formed from a mixture of
100 to 50% by weight of polyether ester type thermoplastic elastomer having a glass transition temperature of not more than xe2x88x9225xc2x0 C. as determined by differential thermal analysis (DSC); and
0 to 50% by weight of ethylene-(meth)acrylate copolymer ionomer having a flexural modulus of 200 to 400 MPa; and
the cover is formed from ethylene-(meth)acrylate copolymer ionomer having a flexural modulus of 200 to 450 MPa and a Shore D hardness of 55 to 68.
In Japanese Patent No. 2658811, a three-piece solid golf ball of which an intermediate layer is placed between a center core and a cover is described. The center core has a diameter of not less than 26 mm, a specific gravity of less than 1.4 and a JIS-C hardness of not more than 80, the intermediate layer has a thickness of not less than 1 mm, a specific gravity of less than 1.2 and a JIS-C hardness of less than 80, and the cover has a thickness of 1 to 3 mm and a JIS-C hardness of not less than 85.
In Japanese Patent Kokai Publication No. 305114/1998, a golf ball of which an intermediate layer is placed between a solid core and a cover, of which the surface of the cover has many dimples, is described. The core has a surface hardness in Shore D hardness of not more than 48, the intermediate layer has a hardness in Shore D hardness of 53 to 60 and the hardness of the intermediate layer is higher than the surface hardness of the core by not less than 8, the cover has a hardness in Shore D hardness of 55 to 65 and the hardness of the cover is higher than that of the intermediate layer, the dimples are consisted of two types having different diameter and/or depth from each other, the total number of the dimples is within the range of 370 to 450, the dimples cover at least 63% of the ball surface, and the index Dst of the overall dimple surface area is at least 4.
However, in the golf balls described above, it has been problem that when hit at low head speed by a driver or iron club, high launch angle and low spin amount are not accomplished, and flight performances is degraded, or shot feel is hard and poor. In addition, the problem has not been considered.
A main object of the present invention is to provide a three-piece solid golf ball, of which flight distance is improved by accomplishing high launch angle and low spin amount in initial flight performance, while maintaining soft and good shot feel, when hit at low head speed in addition to high and middle head speed by a driver or an iron club.
According to the present invention, the object described above has been accomplished by providing a three-piece solid golf ball, of which an intermediate layer is placed between a center and a cover, and by adjusting a deformation amount, hardness and hardness distribution of the center, a hardness and thickness of the intermediate layer, a hardness and thickness of the cover, and a hardness distribution from the center to the cover to specified ranges, thereby providing a three-piece solid golf ball, of which flight distance is improved by accomplishing high launch angle and low spin amount in initial flight performance, while maintaining soft and good shot feel when hit at low head speed.
This object as well as other objects and advantages of the present invention will become apparent to those skilled in the art from the following description with reference to the accompanying drawings.